Effect of different ceramic powders and sintering temperatures on properties of resin-infused ceramics

OBJECTIVES: To investigate the effect of different ceramic powders on the microstructure, biaxial flexural strength, hardness and absorption coefficient of resin-infused zirconia and alumina, to investigate the effect of sintering temperatures on the microstructure, biaxial flexural strength, hardness and absorption coefficient of resin-infused spinel, and to investigate the effect of cyclic fatigue on biaxial flexural strength of resin-infused ceramics. MATERIALS: Resin-infused zirconia, resin-infused alumina and resin-infused spinel METHODS: Zirconia powders (TOSOH TZ and Zpex) and alumina powders (Almatis and Taimei) were dry-pressed in a stainless steel mold to fabricate ceramic discs. Discs were sintered to 1050°C. McMaster-Carr partially sintered alumina rod was cut into discs of 1.5 mm thickness. Ceranova spinel discs were divided into two groups sintered at two different temperatures (1250°C and 1350°C). Density of each disc was measured and a total of 8 discs per group were prepared. Specimens were silane treated, and then infused with an UDMA mixture under vacuum. Infused specimens were cured with an Isopress machine at pressures of 20,001 psi. Biaxial flexural strength was measured using an Instron Universal Testing machine at 0.5 mm/min crosshead speed. Another group was subjected to cyclic fatigue (50,000 cycles) before biaxial flexural strength test. Hardness was tested using vickers microhardness indenter (Buehler Micromat 2003). Spectrophotometer was used for direct transmission measurements and absorption coefficient was calculated. Microstructure of each group was investigated with a scanning electron microscope (SEM). The data were analyzed using one-way ANOVA and Tukey multiple comparisons. T-test was used to compare biaxial flexural strength of each group before and after cyclic fatigue. RESULTS AND CONCLUSIONS: Using different ceramic powders had no significant effect on the biaxial flexural strength and absorption coefficient of resin-infused zirconia. Resin-infused Zpex zirconia had significantly greater microhardness than resin-infused Tz zirconia. Resin-infused MCM alumina had significantly greater biaxial flexural strength than resin-infused Almatis alumina. Resin-infused MCM and Taimei alumina had significantly greater microhardness than resin-infused Taimei alumina. Resin-infused Almatis alumina had significantly greater absorption coefficient than resin-infused Taimei alumina. Cyclic fatigue had significantly reduced the biaxial flexural strength of resin-infused Tz zirconia, Almatis alumina and spinel 1250 but had no significant effect on the rest of the groups. Increasing sintering temperature of resin-infused spinel from 1250°C to 1350°C had no significant effect on biaxial flexural strength and absorption coefficient but it significantly increased the microhardness.2019-09-26T00:00:00

The effect of prolonged formalin fixation on the staining characteristics of archival human brain tissue

Background: Neurodegenerative disorders include wide range of conditions, which affect millions of people worldwide. Unfortunately, they are incurable and irreversibly progressive. Immunohistochemical staining of paraffin-fixed tissues for both diagnostic and research purposes are widely used. However, large amount of brain tissues are fixed but little is known about whether they are suitable for retrospective studies. The study aimed at investigating the effects of prolonged formalin fixation time on immunohistochemical expression of some common neurodegenerative markers in archival brain specimens.  Materials and methods: Twenty brain specimens were obtained from hu- man cadavers in the Anatomy Department of King Abdulaziz University that were prefixed in 10% formalin. They were divided into two equal groups according to time of fixation: group 1 — less than 1 year, group 2 — up to 20 years. Histological examination of white and grey matter was done using haematoxylin and eosin, luxol fast blue (LFB) for myelin staining, Con- go red for amyloid plaques, CD 68 for microglial cells, tenascin-C (large ex- tracellular matrix glycoprotein) and caspase 3 antibody for apoptotic cells.  Results: For both groups, corpus callosum sections displayed myelination with LFB staining. The distribution of CD 68 positive microglial cells was evi- dent in frontal and temporal grey matter, but not in corpus callosum sections. Strongly positive masses were seen in Congo red-stained frontal and temporal sections. Anti-caspase 3 immunostaining revealed positively stained neurons. Conclusions: Histological and immunohistochemical techniques yielded repro- ducible staining results when applied to human brain tissue stored in formalin for long periods; so they can be used in well preserved biobank material which are the most targeting research areas in neuropathology.

The effect of desiccation on water sorption,solubility and hygroscopic volumetric expansion of dentine replacement materials

ObjectiveTo evaluate water sorption, solubility and hygroscopic expansion and the effect of desiccation for a calcium silicate-based material, a conventional glass ionomer, and a resin-modified glass ionomer.MethodsWater sorption, solubility and hygroscopic expansion of Biodentine™ (BD), GC Fuji IX GP® FAST (FJ), and Ionolux (IO) were tested under two pre-storage conditions: with desiccation and without desiccation. Disc-shaped samples (n = 5) were immersed in water and weighed at different time intervals (1 h, 24 h, 3 d, 7 d and 30 d) and hygroscopic expansion was recorded at 7 d and 30 d. Data were analysed using Factorial repeated measures ANOVA, one-way/two-way ANOVA, Independent samples t-test and Tukey’s post hoc test (α = 0.05).ResultsWith desiccation, sorption of IO and FJ was 124.33 μg/mm3 and 79.97 μg/mm3 respectively. Solubility was −12.36 μg/mm3 for IO and −20.19 μg/mm3 for FJ. Hygroscopic expansion was 3.01% for IO and −2.35% for FJ.Without desiccation, sorption was in the order: IO ˃ BD ˃ FJ (130.35 μg/mm3, 122.07 μg/mm3, and 107.21 μg/mm3 respectively), while solubility order was: BD ˃ FJ ˃ IO (154.83 μg/mm3, 88.82 μg/mm3, and 25.67 μg/mm3 respectively). IO and FJ showed significant difference in sorption and solubility between the two pre-storage treatment groups (p ˂ 0.005). Hygroscopic expansion was in the order: IO ˃ BD ˃ FJ.SignificanceBD had the highest solubility while IO had the least. The relatively stable polymeric resin in IO may contribute to its low solubility but high hygroscopic expansion. Desiccation had significant effect on sorption, solubility and volumetric expansion of water-based materials.KeywordsSorptionSolubilityHygroscopic expansionDesiccationDentine replacemen

The possible protective effects of virgin olive oil and Nigella sativa seeds on the biochemical and histopathological changes in pancreas of hyperlipidaemic rats

Background: Hyperlipidaemia is a risk factor for the development and progression of atherosclerosis and is linked to various diseases. This study was done to evaluate the possible protective effects of virgin olive oil and Nigella sativa seeds on the biochemical and histopathological changes which occurred in the pancreas of the rats. The study lasted 8 weeks and included 24 albino rats that were divided into four groups (6 rats each); Group I — control group, fed with normal standard diet, Group II — fed with high fat diet (HFD), Group III — fed with HFD and virgin olive oil, Group IV — fed with HFD and Nigella sativa seeds powder. Materials and methods: After finishing the experiment, blood samples were collected and assessed for the lipid profile, fasting blood glucose, pancreatic amylase and insulin levels. Then, the rats were sacrificed and the pancreata were extracted and slices of them were processed for histological examination using haematoxylin stain and Masson’s trichrome stain. Small fragments from the tail of the pancreata were extracted and processed for electron microscopic examination. The statistical analysis of the data using the appropriate statistical tests was also conducted. Results: In the present study, the serum lipid profile in hyperlipidaemic rats was ameliorated in rats fed on high fat diet with virgin olive oil or Nigella sativa seed powder, which was reflected by a significant decrease in total cholesterol, low-density lipoprotein-cholesterol and triglycerides. Moreover, Nigella sativa decreased high-density lipoprotein (HDL), while virgin olive oil significantly increased HDL. Also a significant decrease in the serum levels of blood glucose and amylase and a significant increase in insulin levels were present in these groups. The histological and ultrastructural results revealed regeneration of the exocrine and endocrine parts of the pancreatic tissues from the hyperlipidaemic rats fed with virgin olive oil or Nigella sativa seeds. Conclusions: In this study, the biochemical results were paralleled to the histological and ultrastructural results; therefore, it could be concluded that virgin olive oil and Nigella sativa seeds had antihyperlipidaemic and hypoglycaemic effects and they could protect the pancreas from hyperlipidaemia-induced injury. Daily consumption of virgin olive oil and Nigella sativa seeds in the diet is highly recommended

The molecular basis of enhanced glucose transporter, SGLT1, expression in the diabetic intestine

Dietary carbohydrates are hydrolyzed in the small intestine ultimately, by the brush-border membrane disaccharidases (sucrase, maltase and lactase) into monosaccharides: D-glucose, D-galactose and D-fructose. D-glucose and D-galactose are transported across the brush border membrane (BBM) from the intestinal lumen into enterocytes by the Na+- dependent glucose transporter 1, SGLT1, while D-fructose is transported by GLUT5. These monosaccharides, exit the cell across the baso-lateral membrane (BLM) into the systemic circulation via the facilitated monosaccharide transporter, GLUT2. SGLT1 regulation is vital for the provision of glucose to the body and for maintaining glucose homoeostasis. The expression and activity of SGLT1 are adaptively regulated by dietary sugars in most species studied. The intestinal capacity to absorb glucose is maintained via basal level of SGLT1 expression. However, this capacity becomes limited when the luminal carbohydrates exceed a threshold level, leading to up-regulation of SGLT1. Previous work in our laboratory has shown that luminal sugar concentration, when above a threshold, is detected by the intestinal glucose sensor, consisting of two subunits, Taste 1 receptor 2 (T1R2) and 3 (T1R3) expressed in enteroendocrine L-cells. This activates a pathway, in endocrine cells, leading to secretion of the gut hormone glucagon like peptide 2 (GLP-2), known to up-regulate SGLT1 expression. Binding of GLP-2 to its receptor on the enteric neurons induces a neuronal response evoking secretion of vasoactive intestinal peptide (VIP) and/or Pituitary adenylate cyclase-activating polypeptide (PACAP) by sub-mucosal plexus. Binding of VIP/PACAP to their receptor VPAC1 (VIP and PACAP receptor type 1) on the basolateral membrane of absorptive enterocytes leads to increased concentration of intracellular cAMP which in turn enhances the half-life of SGLT1 mRNA, increasing the number of SGLT1 proteins per enterocytes. In diabetes, the intestinal capacity for glucose absorption is enhanced complicating the aetiology of the disease. This enhanced expression is independent of either luminal sugar and blood glucose concentrations or insulin levels. The work in this thesis was aimed at identify molecular basis of enhanced SGLT1 expression in the diabetic intestine using intestinal tissues from rats with experimentally induced diabetes and biopsies from the intestine of human diabetics. The data indicate that increased SGLT1 expression is due to dysregulation of pathway controlling SGLT1 expression

The Effect of Simulated Chewing on the Surface Roughness of Direct and Indirect Resin-Composites Opposed by Zirconia: An In Vitro Study

PURPOSE: To assess the surface roughness of two different light-cured resin-composites when opposed by monolithic zirconia after simulated mastication. MATERIALS AND METHODS: Materials included a direct restorative nanohybrid (n = 10) and an indirect microhybrid (n = 10) resin-composite (Tetric EvoCeram and Sinfony, respectively). The antagonist material was 3 mol% yttria-stabilized tetragonal zirconia polycrystalline ceramic. Each material was subjected to in vitro chewing against zirconia using a chewing simulator for 250,000 cycles. A 3D profilometer was used to assess the surface roughness parameters of each resin-composite before and after the simulated chewing. Independent t-test and paired sample t-test were performed to compare roughness values for both materials and to compare baseline and after chewing simulation values (p = 0.05). RESULTS: Sinfony showed significantly greater roughness values compared to Tetric EvoCeram (p ≤ 0.025) before and after simulated chewing, except for Sa and Sv parameters after simulated chewing where the difference between the two materials was insignificant (p = 0.06 and 0.89, respectively). Surface roughness increased for both materials after simulated chewing compared to baseline values, but the difference was insignificant (p ≥ 0.065). However, Sa (p = 0.04) and Sv (p = 0.012) for Tetric EvoCeram were significantly higher after compared to before chewing simulation. CONCLUSION: Tetric EvoCeram had a smoother surface than Sinfony before and after simulated chewing. Surface roughness for both materials was higher after simulated chewing compared to baseline values which represent surface damage that was significant for Tetric EvoCeram while Sinfony showed better resistance

The pattern of branching and intercommunications of the musculocutaneous nerve for surgical issues: anatomical study

Background: The aim of the present work was to provide evidence about the anatomical variations as regard the origin, distribution, and branching pattern of the musculocutaneous nerve (MCN). Materials and methods: Brachial plexus was dissected in 40 upper limbs of 20 male adult cadavers. The pattern of the musculocutaneous nerve was photographed by a digital camera. Results: The location and length of the nerve branches between left and right arms were recorded and statistically analyzed. In (90%) of specimens the MCN originates from the lateral cord of the brachial plexus, in (5%) it arose from the median nerve (MN), while in the remaining (5%) specimen, it was absent. The musculocutaneous nerve pierced the coracobrachialis muscle in 90% of specimens, and in the remaining (10%) did not pierce it. The motor branches to biceps brachii muscle were categorized into: Type 1 (90%): one branch that divides to supply the two heads of biceps; Type 2 (5%): double branches, innervating each head of biceps separately. The motor branches to brachialis muscle were categorized into: Type 1 (82.9%): one branch; Type 2 (14.2%): double branches and Type 3 (2.9%): three branches that innervating brachialis muscle. Communications between the MCN and the MN were observed in 35% of specimens. Conclusions: The knowledge of the common and uncommon musculocutaneous nerve variations is important especially to the surgeons for carrying out surgical procedures in axilla and arm

An Overview Of Disinfectant And Antiseptic Techniques And Its Important In Nursing, Dentistry And Operating Theatre

In contemporary Oral and Maxillofacial surgery, intricate surgical and aesthetic treatments are performed, which are accompanied by a higher likelihood of infection complications. Thus, in order to guarantee improved results of the surgical treatments, it is imperative that adequate measures are implemented to reduce the occurrence of related infections. The infection control practices encompass meticulous scrubbing techniques for both the patient and the operator, adherence to specific protocols by the operating personnel during procedures, careful handling of instruments, and the maintenance of an aseptic environment throughout the entire procedure. The primary objective of this chapter is to present details regarding the preoperative, operative, and post-operative protocols that must be followed to enhance the safety of patients having surgical procedures